1. Technical Field
The present invention relates to a carbon nanotube-graphene composite, and more particularly, to a carbon nanotube-graphene composite having a patterned layer of aligned carbon nanotubes formed on a graphene layer.
2. Description of Related Art
Global warming and petroleum crisis have become pressing issues to human sustainability and stimulated numerous attempts to seek for mitigation. Researches addressing these concerns may be divided into several categories: exploiting alternative energy resources, developing energy scavenging technology to harvest the waste work in our daily life, or constructing more efficient energy storage devices. The last one, at present, focuses much on the field of “supercapacitor,” which generally refers to two distinct types of capacitor, that is, the electrical double-layer capacitors (EDLC) and the pseudocapacitors. The former operates by the separation of charge in a Helmholtz double layer at the interface between the surface of a conductor electrode and an electrolytic solution electrolyte; the latter utilizes the redox reactions electrosorbtion or intercalation on the surface of the electrode.
With regard to the electrical double-layer capacitors, since the capacitance value is determined by charges adsorbed on the surface of the electrode, materials with high specific surface area have become prominent candidates. Of these, vertically aligned carbon nanotube array drew much attention. However, the bonding strength between the vertically aligned carbon nanotubes and the underlying substrate is often weak, and the carbon nanotubes may be peeled off from the substrate after a limited number of charge and discharge cycles.